Influenza is an acute respiratory illness of global importance. Despite international attempts to control influenza virus outbreaks through vaccination influenza infections remain an important cause of morbidity and mortality. Worldwide influenza pandemics have occurred at irregular and previously unpredictable intervals throughout history and it is expected that they will continue to occur in the future. The impact of pandemic influenza is substantial in terms of morbidity, mortality and economic cost.
Influenza vaccines remain the most effective defense against influenza virus, but because of the ability of the virus to mutate and the availability of non-human host reservoirs it is expected that influenza will remain an emergent or re-emergent infection. Global influenza surveillance indicates that influenza viruses may vary within a country and between countries and continents during an influenza season. Virologic surveillance is of importance in monitoring antigenic shift and drift. Disease surveillance is also important in assessing the impact of epidemics. Both types of information have provided the basis of vaccine composition and the correct use of antivirals. However, to date there has been only annual post hoc hematological classification of the increasing number of emerging influenza virus strains, and no specific chemical structure of the viruses has been identified as an indicator of approaching influenza epidemic or pandemic. Currently, the only basis for annual classification of influenza virus as active, inactive or prevalent in a given year is the activities of the virus hemagglutinin and neuramimidase proteins. No influenza viral chemical structure has been identified that can be used for quantitative warning of epidemics or pandemics or to design more effective and safer vaccines.
Because of the annual administration of influenza vaccines and the short period of time when a vaccine can be administered, strategies directed at improving vaccine coverage are of critical importance.
Another disease which has proved difficult to treat and for which there is no effective vaccine is malaria. Malaria causes much physical and economic hardship in tropical regions. Malaria is caused by Plasmodium falciparum, which has proved to be extremely resistant to treatment and to date, a vaccine for malaria remains elusive. Thus, there is a need for effective malaria vaccines and methods of treating or preventing the disease.